Integrated circuit

ABSTRACT

According to one embodiment, provided are an amplifier transistor configured to amplify an input signal; a biasing circuit configured to set a bias voltage in such a manner as to allow the amplifier transistor to perform amplification; an electrostatic protective circuit configured to set the bias voltage for the amplifier transistor in such a manner as to make the amplifier transistor to turn off based on voltage to be applied to the amplifier transistor; and a switching circuit configured to switch the bias voltage for the amplifier transistor based on a power supply condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2011-237888, filed on Oct. 28, 2011; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments disclosed herein generally relate to integrated circuits.

BACKGROUND

As a preventive method for protecting integrated circuits fromelectrostatic destruction due to static electricity, a protective deviceis provided in some cases for diverting surge current. Even in this caseof providing a protective device to divert surge current, the integratedcircuit may be subject to static destruction if the integrated circuitincludes a path that allows surge current to pass therethrough.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram illustrating the overall configuration of anintegrated circuit according to a first embodiment;

FIG. 2 is a circuit diagram illustrating a method of connecting anamplifier circuit 1 of FIG. 1 with external components 12 and 13;

FIG. 3 is a circuit diagram illustrating the overall configuration of anintegrated circuit according to a second embodiment; and

FIG. 4 is a circuit diagram illustrating the overall configuration of anintegrated circuit according to a third embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, integrated circuit includes anamplifier transistor, a biasing circuit, an electrostatic protectivecircuit, and a switching circuit. The amplifier transistor is configuredto amplify input signals. The biasing circuit is configured to set biasvoltage to allow the amplifier transistor to perform amplification. Theelectrostatic protective circuit is configured to set the bias voltagefor the amplifier transistor such that the amplifier transistor is to beturned off based on voltage to be applied to the amplifier transistor.The switching circuit is configured to switch the bias voltage for theamplifier transistor based on a power supply condition.

Integrated circuits according to embodiments are described below withreference to the drawings. It is to be noted that these embodiments arenot intended to limit the scope of the present invention.

First Embodiment

FIG. 1 is a circuit diagram illustrating the overall configuration of anintegrated circuit according to a first embodiment.

In FIG. 1, the integrated circuit includes an amplifier circuit 1, anelectrostatic protective circuit 2, a switching circuit 3, and a biasingcircuit 4. The integrated circuit also includes diodes D1 to D8 aselectrostatic protective devices.

The amplifier circuit 1 is capable of amplifying input signals. Theamplifier circuit 1 herein includes amplifier transistors M1 and M2,resistors R1 and R2, an inductor L1, and capacitors C1 and C2. Forexample, an n-channel field effect transistor (FET) may be used for theamplifier transistors M1 and M2.

The amplifier transistors M1 and M2 are connected in series to eachother. The source of the amplifier transistor M1 is coupled to a groundterminal GND_LNA through the inductor L1. The capacitor C1 is connectedbetween the gate and source of the amplifier transistor M1. The gate ofthe amplifier transistor M1 is connected with the resistor R1 so as tobe applied with bias voltage BA1 through the resistor R1. The gate ofthe amplifier transistor M1 is connected with an input terminal LNA_INso as to allow input signals to be inputted through the input terminalLNA_IN.

The drain of the amplifier transistor M2 is connected to an outputterminal LNA_OUT. The capacitor C2 is connected between the gate of theamplifier transistor M2 and the ground terminal GND_LNA. The gate of theamplifier transistor M2 is connected with the resistor R2 so as to beapplied with bias voltage BA2 through the resistor R2.

The biasing circuit 4 is capable of setting the bias voltages BA1 andBA2 so as to allow the amplifier transistors M1 and M2 to performamplification. The biasing circuit 4 herein is supplied with powervoltage through a power supply terminal VDD_LNA. The bias voltages BA1and BA2 are generated at the biasing circuit 4. The bias voltage BA1 isapplied to the gate of the amplifier transistor M1 through the resistorR1. The bias voltage BA2 is applied to the gate of the amplifiertransistor M2 through the resistor R2.

The electrostatic protective circuit 2 is capable of setting the biasvoltage BA1 for the amplifier transistor M1 such that the amplifiertransistor M1 is to be turned off based on the voltage to be applied tothe amplifier transistors M1 and M2. The electrostatic protectivecircuit 2 herein includes a switching transistor M3, inverters N2 andN3, and a resistor R3. For example, an n-channel FET may be used for theswitching transistor M3. The drain of the switching transistor M3 iscoupled to the gate of the amplifier transistor M1 through the resistorR1. The source of the switching transistor M3 is connected to the groundterminal GND_LNA. The inverters N2 and N3 are connected in series toeach other. The input of the inverter N2 is coupled to the power supplyterminal VDD_LNA through the resistor R3. The output of the inverter N3is connected to the gate of the switching transistor M3. The invertersN2 and N3 are supplied with power voltage through the power supplyterminal VDD_LNA.

The switching circuit 3 is capable of switching the bias voltage BA1 forthe amplifier transistor M1 based on the supply condition of powervoltage VDDC. The switching circuit 3 herein includes an inverter N1.The inverter N1 is supplied with the power voltage VDDC. Power-onsignals PS are inputted to the inverter N1. The output of the inverterN1 is connected to the input of the inverter N2.

The diode D5 is connected between the output terminal LNA_OUT and thepower supply terminal VDD_LNA. The diodes D6 to D8 are in serialconnection. Thus, the series circuit of the diodes D6 to D8 is connectedbetween the power supply terminal VDD_LNA and the ground terminalGND_LNA. The diodes D1 and D2 are connected in antiparallel to eachother. The diodes D3 and D4 are connected in antiparallel to each other.The antiparallel circuit of the diodes D1 and D2 and the antiparallelcircuit of the diodes D3 and D4 are connected in series to each other.This series circuit is connected between the ground potential GNDC ofthe inverter N1 and the ground terminal GND_LNA.

FIG. 2 is a circuit diagram illustrating a method of connecting theamplifier circuit 1 of FIG. 1 with external components 12 and 13.

In FIG. 2, the amplifier circuit 1 and a regulator 7 are mounted on asemiconductor chip 11. The regulator 7 is capable of converting powervoltage VDD1 to power voltage VDD2. The regulator 7 herein includes acomparator PA. The comparator PA is supplied with the power voltage VDD1so as to compare the power voltage VDD2 with reference voltage ref.

The gate of the amplifier transistor M1 is connected to an inputterminal TI. The drain of the amplifier transistor M2 is connected to anoutput terminal TO. The source of the amplifier transistor M1 is coupledto a ground terminal TG through the inductor L1. The output terminal ofthe regulator 7 is connected to a power supply terminal TD.

The input terminal TI is connected with an external component 12 forobtaining matching with input signals In. An external component 13 forobtaining matching with output signals Out is connected between theoutput terminal TO and the power supply terminal TD. The externalcomponent 12 herein includes inductors L11 and L12 and a capacitor C11.The input signals In are inputted to the gate of the amplifiertransistor M1 sequentially through the inductor L11 and the capacitorC11. The connection point between the inductor L11 and the capacitor C11is grounded through the inductor L12.

The external component 13 includes an inductor L13, a capacitor C12, anda resistor R11. The inductor L13 and the resistor R11 are connected toeach other. The power voltage VDD2 outputted from the comparator PA issupplied to the drain of the amplifier transistor M2 through theparallel circuit of the inductor L13 and the resistor R11. The outputsignals Out are outputted from the drain of the amplifier transistor M2through the capacitor C12.

The input terminal TI, the output terminal TO, the power supply terminalTD, and the ground terminal TG of the amplifier circuit 1 are exposed tothe outside of the semiconductor chip 11. The input terminal TI isconnected to the gate of the amplifier transistor M1 without anintervening resistor. The output terminal TO is connected to the drainof the amplifier transistor M2 without an intervening resistor. Theground terminal TG is connected to the source of the amplifiertransistor M1 without an intervening resistor. Hence, surge current isdirectly inputted to the amplifier transistors M1 and M2.

It is to be noted that the electrostatic protective circuit 2, theswitching circuit 3, and the biasing circuit 4 that are illustrated inFIG. 1 may be mounted on the semiconductor chip 11.

In FIGS. 1 and 2, power is not supplied to the semiconductor chip 11before implementation of the semiconductor chip 11 on a circuit board.Hence, power voltage is not supplied to the biasing circuit 4 and theinverter N1, and the gate voltages of the amplifier transistors M1 andM2 and the gate voltage of the switching transistor M3 are thusinconstant.

At this time, suppose surge voltage is applied between the outputterminal LNA_OUT and the ground terminal GND_LNA. If the amplifiertransistors M1 and M2 are off in this state, surge current flows fromoutput terminal LNA_OUT to the ground terminal GND_LNA through thediodes D5 to D8. Thus, surge current does not flow into the amplifiertransistors M1 and M2, and the amplifier transistors M1 and M2 areprotected from destruction.

Herein, if surge voltage is applied to the output terminal LNA_OUT, thepotential of the power supply terminal VDD_LNA rises through the diodeD5. When the potential of the power supply terminal VDD_LNA rises enoughto make the biasing circuit 4 into operation, the bias voltages BA1 andBA2 are set at the biasing circuit 4 so as to turn the amplifiertransistors M1 and M2 on. If the amplifier transistors M1 and M2 areturned on upon application of surge voltage to the output terminalLNA_OUT, surge current flows into the amplifier transistors M1 and M2,leading to destruction of the amplifier transistors M1 and M2.

Meanwhile, the potential of the power supply terminal VDD_LNA isdetected through the resistor R3, and the voltage detected through theresistor R3 is inputted to the inverter N2. With power being notsupplied to the semiconductor chip 11, a path of current to flow fromthe power supply terminal VDD_LNA to the resistor R3 is not generated.This allows the potential of the power supply terminal VDD_LNA to beinputted to the inverter N2 without involving voltage drop that may beotherwise made by the resistor R3. The inverters N2 and N3 are drivenbased on the voltage detected through the resistor R3, such that thepotential of the power supply terminal VDD_LNA is applied to the gate ofthe switching transistor M3. Herein, rise in potential of the powersupply terminal VDD_LNA upon application of surge voltage to the outputterminal LNA_OUT makes the switching transistor M3 to turn on. Thus, thebias voltage BA1 for the amplifier transistor M1 becomes 0 V and thegate potential of the amplifier transistor M1 becomes 0 V. Hence, theamplifier transistor M1 is turned off, allowing for prevention of surgecurrent from flowing into the amplifier transistors M1 and M2.

For example, suppose a surge voltage of 6 V is applied between theoutput terminal LNA_OUT and the ground terminal GND_LNA and the surgevoltage is applied to the power supply terminal VDD_LNA through thediode D5 to bring the potential of the power supply terminal VDD_LNA to4.5 V. At this time, a power voltage of 4.5 V is applied to the biasingcircuit 4, and bias voltages BA1 and BA2 of 0 V to 4.5 V are generatedat the biasing circuit 4.

Meanwhile, the potential of the power supply terminal VDD_LNA istransmitted to the inverter N2 through the resistor R3, and a voltage of4.5 V is inputted to the inverter N2. When the voltage of 4.5 V isinputted to the inverter N2, the gate potential of the switchingtransistor M3 is set to 4.5 V through the inverters N2 and N3. Thus,gate-to-source voltage Vgs3 of the switching transistor M3 becomes 4.5V, causing the switching transistor M3 to turn on. As a result, the biasvoltage BA1 for the amplifier transistor M1 becomes 0 V, and the biasvoltage BA1 is applied to the gate of the amplifier transistor M1through the resistor R1, bringing the gate-to-source voltage Vgs1 of theamplifier transistor M1 to 0 V and turning the amplifier transistor M1off. At this time, assuming the amplifier transistor M2 is turned on andthe drain-to-source voltage Vds2 of the amplifier transistor M2 hasbecome 0 V, the drain-to-source voltage Vds1 of the amplifier transistorM1 makes 6 V.

Meanwhile, when the semiconductor chip 11 is mounted on a circuit board,power is supplied to the semiconductor chip 11. Thus, power voltage VDDCis supplied to the inverter N1, and power voltage is supplied to thebiasing circuit 4 through the power supply terminal VDD_LNA.

When power-on signals PS reach High level, the outputs PS_B from theinverter N1 come to Low level. When power voltage is supplied to thepower supply terminal VDD_LNA, the power voltage of the power supplyterminal VDD_LNA is lowered through the resistor R3 with current beingextracted to the inverter N1 through the resistor R3, and the outputsPS_B from the inverter N1 are maintained at Low level. Then, theinverters N2 and N3 are driven based on the outputs PS_B from theinverter N1, such that the potential of the ground terminal GND_LNA isapplied to the gate of the switching transistor M3. This makes theswitching transistor M3 to turn off, and the bias voltage BA1 for theamplifier transistor M1 is set through the biasing circuit 4.

When power voltage is supplied to the biasing circuit 4, the biasvoltages BA1 and BA2 are set so as to allow the amplifier transistors M1and M2 to perform amplification. Then, input signals are applied to thegate of the amplifier transistor M1, causing current to flow into theamplifier transistors M1 and M2 in response to the input signals, suchthat the output signals corresponding to the current are outputtedthrough the output terminal LNA_OUT. The amplifier transistor M2 hereinmay be so configured that drain current extracted from the amplifiertransistor M1 is kept from returning to the amplifier transistor M1.

The source current of the amplifier transistor M1 is transformed tovoltage through the inductor L1 and fed back to the gate of theamplifier transistor M1 through the capacitor C1, such that matching isattained and noise is reduced.

For example, assuming the power voltage VDD1 is 3.3 V upon applicationof power to the semiconductor chip 11, the voltage is converted to apower voltage VDD2 of 1.2 V at the regulator 7 and is supplied to thedrain of the amplifier transistor M2 through the external component 13.Thus, the potential of the output terminal LNA_OUT is set to 1.2 V.Further, the power voltage VDD2 is applied to the power supply terminalVDD_LNA, so that the potential of the power supply terminal VDD_LNA isset to 1.2 V.

When the power voltage VDDC is supplied to the inverter N1 and thepower-on signals PS reach High level, the outputs PS_B from the inverterN1 become 0 V. Then, current is drawn into the inverter N1 from thepower supply terminal VDD_LNA through the resistor R3, a voltage drop by1.2 V takes place at the resistor R3, and the potential of the powersupply terminal VDD_LNA is maintained at 1.2 V.

With the potential of the power supply terminal VDD_LNA maintained at1.2 V, a power voltage of 1.2 V is applied to the biasing circuit 4, anda bias voltage BA1 of 0.4 V is generated at the biasing circuit 4, whilea bias voltage BA2 of 0.8 V is also generated.

When the outputs PS_B from the inverter N1 become 0 V, the gatepotential of the switching transistor M3 is set to 0 V through theinverters N2 and N3. Thus, the gate-to-source voltage Vgs3 of theswitching transistor M3 becomes 0 V, causing the switching transistor M3to turn off. As a result, the gate potential of the amplifier transistorM1 becomes 0.4 V, and the gate-to-source voltage Vgs1 of the amplifiertransistor M1 becomes 0.4 V. Further, the drain-to-source voltage Vds1of the amplifier transistor M1 becomes 0.4 V. Moreover, the gatepotential of the amplifier transistor M2 becomes 0.8 V, and thegate-to-source voltage Vgs2 of the amplifier transistor M2 becomes 0.4V. In addition, the drain-to-source voltage Vds2 of the amplifiertransistor M2 becomes 0.8 V.

Herein, the switching transistor M3 may be coupled between the sourceside and the gate side of the amplifier transistor M1 so as to make theswitching transistor M3 to turn on upon detection of surge voltage, suchthat the voltage between the source and gate of the amplifier transistorM1 can be set to 0 V. Hence, the amplifier transistor M1 is preventedfrom being turned on upon input of surge voltage, allowing forprevention of surge current from flowing into the amplifier transistorsM1 and M2. Hence, enhanced resistance to electrostatic destruction isachieved with the amplifier transistors M1 and M2.

In addition, detection sensitivity to surge voltage is enhanced byconfiguring such that surge voltage is detected through the resistor R3and the inverters N2 and N3. Moreover, the switching transistor M3 maybe coupled to the gate of the amplifier transistor M1 through theresistor R1, such that parasitic capacitance of the switching transistorM3 is made invisible from the side of the input terminal LNA_IN,allowing for suppression of lowering in gain and noise characteristics.

Further, with the provision of the switching circuit 3, the switchingtransistor M3 can be turned off upon power input, even in the case wherethe switching transistor M3 is turned on based on surge voltage at apoint where power is yet to be inputted; thus, the amplifying functionsof the amplifier transistors M1 and M2 are protected from degradation.

Second Embodiment

FIG. 3 is a circuit diagram illustrating the overall configuration of anintegrated circuit according to a second embodiment.

In FIG. 3, the integrated circuit includes an electrostatic protectivecircuit 5 in place of the electrostatic protective circuit 2 of theintegrated circuit in FIG. 1. The electrostatic protective circuit 5 iscapable of setting the bias voltage BA2 for the amplifier transistor M2such that the amplifier transistor M2 is to be turned off based on thevoltage to be applied to the amplifier transistors M1 and M2. Theelectrostatic protective circuit 5 herein includes a switchingtransistor M4 in place of the switching transistor M3. For example, ann-channel FET may be used for the switching transistor M4. The drain ofthe switching transistor M4 is connected to the gate of the amplifiertransistor M2. The source of the switching transistor M4 is connected tothe ground terminal GND_LNA. The output of the inverter N3 is connectedto the gate of the switching transistor M4.

When surge voltage is applied to the output terminal LNA_OUT beforeimplementation of the semiconductor chip 11 on a circuit board, thepotential of the power supply terminal VDD_LNA rises through the diodeD5. The potential of the power supply terminal VDD_LNA is detectedthrough the resistor R3, and the voltage detected through the resistorR3 is inputted to the inverter N2. The inverters N2 and N3 are drivenbased on the voltage detected through the resistor R3, such that thepotential of the power supply terminal VDD_LNA is applied to the gate ofthe switching transistor M4. Herein, rise in potential of the powersupply terminal VDD_LNA upon application of surge voltage to the outputterminal LNA_OUT makes the switching transistor M4 to turn on. Thus, thebias voltage BA2 for the amplifier transistor M2 becomes 0 V, and thegate potential of the amplifier transistor M2 becomes 0 V. This makesthe amplifier transistor M2 to turn off, allowing for protection of theamplifier transistors M1 and M2 from inflow of surge current.

For example, suppose a surge voltage of 6 V is applied between theoutput terminal LNA_OUT and the ground terminal GND_LNA and the surgevoltage is applied to the power supply terminal VDD_LNA through thediode D5, bringing the potential of the power supply terminal VDD_LNA to4.5 V. At this time, a power voltage of 4.5 V is applied to the biasingcircuit 4, and bias voltages BA1 and BA2 of 0 V to 4.5 V are generatedat the biasing circuit 4.

Meanwhile, the potential of the power supply terminal VDD_LNA istransmitted to the inverter N2 through the resistor R3, and a voltage of4.5 V is inputted to the inverter N2. Upon input of the voltage of 4.5 Vto the inverter N2, the gate potential of the switching transistor M4 isset to 4.5 V through the inverters N2 and N3. This brings thegate-to-source voltage Vgs4 of the switching transistor M4 to 4.5 V,causing the switching transistor M4 to turn on. As a result, the biasvoltage BA2 for the amplifier transistor M2 becomes 0 V and the biasvoltage BA2 is applied to the gate of the amplifier transistor M2, suchthat the gate-to-source voltage Vgs2 of the amplifier transistor M2becomes −0.1 V, causing the amplifier transistor M2 to turn off. At thistime, suppose the gate-to-source voltage Vgs1 of the amplifiertransistor M1 becomes 2 V, that the amplifier transistor M1 is turnedon, and that the drain-to-source voltage Vds1 of the amplifiertransistor M1 has become 0.1 V. In this case, the drain-to-sourcevoltage Vds2 of the amplifier transistor M2 makes 5.9 V. Further, thegate-to-drain voltage Vgd2 of the amplifier transistor M2 makes 5.9 V.

Third Embodiment

FIG. 4 is a circuit diagram of the overall configuration of anintegrated circuit according to a third embodiment.

In FIG. 4, the integrated circuit includes an electrostatic protectivecircuit 6 in place of the electrostatic protective circuit 2 of theintegrated circuit in FIG. 1.

The biasing circuit 4 includes biasing transistors M11 to M16 and acurrent source Iref. For example, a p-channel FET may be used for thebiasing transistors M11 to M13. For example, an n-channel FET may beused for the biasing transistors M14 to M16. The biasing transistors M11to M13 herein are capable of performing current mirror operation. Thebiasing transistor M14 is capable of generating bias voltage BA1 basedon the current mirror operation of the biasing transistor M12. Thebiasing transistors M15 and M16 are capable of generating bias voltageBA2 based on the current mirror operation of the biasing transistor M13.

The sources of the biasing transistors M11 to M13 are connected to thepower supply terminal VDD_LNA. The drain of the biasing transistor M11is coupled to the ground terminal GND_LNA through the current sourceIref. The drain of the biasing transistor M12 is coupled to the groundterminal GND_LNA through the biasing transistor M14. The drain of thebiasing transistor M13 is coupled to the ground terminal GND_LNAsequentially through the biasing transistors M15 and M16. The gates ofthe biasing transistors M11 to M13 are connected to the drain of thebiasing transistor M11. The drain of the biasing transistor M14 isconnected to the gate of the biasing transistor M14 and is also coupledto the gate of the amplifier transistor M1 through the resistor R1. Thedrain of the biasing transistor M15 is connected to the gate of thebiasing transistor M15 and is also coupled to the gate of the amplifiertransistor M2 through the resistor R2. The drain of the biasingtransistor M16 is connected to the gate of the biasing transistor M16.

Further, the electrostatic protective circuit 6 is capable of causingthe amplifier transistors M1 and M2 to turn off based on the voltage tobe applied to the amplifier transistors M1 and M2, and also is capableof keeping the bias voltages BA1 and BA2 to be outputted from thebiasing circuit 4 inconstant.

The electrostatic protective circuit 6 herein includes switchingtransistors M3 to M7, the inverters N2 and N3, and the resistor R3. Forexample, an n-channel FET may be used for the switching transistors M3to M6. For example, a p-channel FET may be used for the switchingtransistor M7. The drain of the switching transistor M5 is connected tothe gate of the amplifier transistor M1. The drain of the switchingtransistor M6 is coupled to the gate of the amplifier transistor M2through the resistor R2. The sources of the switching transistors M5 andM6 are connected to the ground terminal GND_LNA. The gates of theswitching transistors M5 and M6 are connected to the output of theinverter N3. The drain of the switching transistor M7 is connected tothe gates of the biasing transistors M11 to M13. The source of theswitching transistor M7 is connected to the power supply terminalVDD_LNA. The gate of the switching transistor M7 is connected to theoutput of the inverter N2.

Power is not supplied to the semiconductor chip 11 before implementationof the semiconductor chip 11 on a circuit board. Hence, power voltage isnot supplied to the biasing circuit 4 and the inverter N1, and the gatevoltages of the amplifier transistors M1 and M2 and the gate voltages ofthe switching transistors M3 to M7 are thus inconstant.

At this time, suppose surge voltage is applied to the power supplyterminal VDD_LNA. The potential of the power supply terminal VDD_LNA isdetected through the resistor R3, and the voltage detected through theresistor R3 is inputted to the inverter N2. The inverters N2 and N3 aredriven based on the voltage detected through the resistor R3, such thatthe gate potentials of the switching transistors M3 to M6 are set toHigh level, and the gate potential of the switching transistor M7 is setto Low level. This makes the switching transistors M3 to M7 to turn on,and the gate potentials of the amplifier transistors M1 and M2 and ofthe biasing transistors M14 and M15 become 0 V, while the gatepotentials of the biasing transistors M11 to M13 are brought to thepotential of the power supply terminal VDD_LNA. This makes the biasingtransistors M11 to M15 to turn off and the bias voltages BA1 and BA2 arebrought to the potential of the ground terminal GND_LNA, while theamplifier transistors M1 and M2 are turned off, allowing for protectionof the amplifier transistors M1 and M2 from inflow of surge current.

Meanwhile, when the semiconductor chip 11 is mounted on a circuit board,power is supplied to the semiconductor chip 11. Thus, power voltage VDDCis supplied to the inverter N1, and power voltage is supplied to thebiasing circuit 4 through the power supply terminal VDD_LNA.

When the power-on signals PS reach High level, the outputs from theinverter N1 come to Low level. When power voltage is supplied to thepower supply terminal VDD_LNA, the power voltage of the power supplyterminal VDD_LNA is lowered through the resistor R3 with current beingextracted to the inverter N1 through the resistor R3, and the outputsfrom the inverter N1 are maintained at Low level. Then, the inverters N2and N3 are driven based on the outputs from the inverter N1, such thatthe gate potentials of the switching transistors M3 to M6 are set to Lowlevel, and that the gate potential of the switching transistor M7 is setto High level. This makes the switching transistor M3 to M7 to turn off,and the bias voltages BA1 and BA2 for the amplifier transistors M1 andM2 are set through the biasing circuit 4 so as to allow the amplifiertransistors M1 and M2 to perform amplification.

Upon application of input signals to the gate of the amplifiertransistor M1, current flows into the amplifier transistors M1 and M2 inresponse to the input signals, and output signals corresponding to thecurrent is outputted through the output terminal LNA_OUT.

Herein, the amplifier transistors M1 and M2 are turned off upondetection of surge voltage and the bias voltages BA1 and BA2 to beoutputted from the biasing circuit 4 are brought to the potential of theground terminal GND_LNA, such that the amplifier transistors M1 and M2are prevented from being turned on. This allows for prevention of inflowof surge current into the amplifier transistors M1 and M2, and enhancedresistance to electrostatic destruction is achieved with the amplifiertransistors M1 and M2.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1-20. (canceled)
 21. An integrated circuit, comprising: a first amplifier transistor including a gate and a source, the first amplifier configured to amplify an input signal; a biasing circuit configured to supply a bias voltage to the gate of the first amplifier transistor; an electrostatic protective circuit including a first resistance and a first switching transistor, wherein the first resistance is electrically connected between a first power source and a gate of the first switching transistor, and the first switching transistor is electrically connected between the gate and the source of the first amplifier transistor and configured to control the first amplifier transistor.
 22. The integrated circuit according to claim 21, wherein the first switching transistor is configured to input the bias voltage or a second power source to the gate of the first amplifier transistor.
 23. The integrated circuit according to claim 21, wherein the first resistance is connected between the first power supply and the gate of the first switching transistor via a first inverter and a second inverter.
 24. The integrated circuit according to claim 23, further comprising: an inductor connected to the source of the first amplifier transistor, and a capacitor connected between the source and the gate of the amplifier transistor.
 25. The integrated circuit according to claim 24, further comprising: a second amplifier transistor connected in series to the first amplifier transistor.
 26. The integrated circuit according to claim 25, wherein a drain of the second amplifier transistor is electrically connected to the first power source via a diode, and the first power source is electrically connected to the second power source via a plurality of diodes.
 27. The integrated circuit according to claim 26, wherein a drain of the first switching transistor is electrically connected to the gate of the first amplifier transistor via a second resistance.
 28. The integrated circuit according to claim 26, wherein the first amplifier transistor, the second amplifier transistor, and the first switching transistor are n-channel field effect transistors.
 29. The integrated circuit according to claim 21, wherein the biasing circuit includes a first biasing transistor, a second biasing transistor, and a third biasing transistor; a source of the first biasing transistor and a source of the second biasing transistor are connected to the first power source; and a gate of the first biasing transistor, a drain of the first biasing transistor, and a gate of the second biasing transistor are connected in common; and wherein the electrostatic protective circuit includes a first inverter, a second inverter, and a second switching transistor; the first resistance is connected to an input of the first inverter; an output of the first inverter is connected to an input of the second inverter; an output of the second inverter is connected to the gate of the first switching transistor; a source of the second switching transistor is connected to the first power source; a drain of the second switching transistor is connected to the gate of the first biasing transistor; and a gate of the second switching transistor is connected to the output of the first inverter.
 30. The integrated circuit according to claim 29, wherein a drain of the second biasing transistor, a drain of the third biasing transistor, a gate of the third biasing transistor, and a drain of the first switching transistor are connected in common, and the bias voltage is output from the drain of the second biasing transistor.
 31. The integrated circuit according to claim 30, further comprising: an inductor connected to the source of the first amplifier transistor, and a capacitor connected between the source and the gate of the amplifier transistor.
 32. The integrated circuit according to claim 31, further comprising: a second amplifier transistor connected in series to the first amplifier transistor.
 33. The integrated circuit according to claim 32, wherein a drain of the second amplifier transistor is electrically connected to the first power source via a diode, and the first power source is electrically connected to the second power source via a plurality of diodes.
 34. The integrated circuit according to claim 33, wherein the drain of the first switching transistor is electrically connected to the gate of the first amplifier transistor via a second resistance.
 35. The integrated circuit according to claim 34, wherein the biasing circuit further includes a fourth biasing transistor, a fifth biasing transistor, and a sixth biasing transistor, a source of the fourth biasing transistor is connected to the first power source; a gate of the fourth biasing transistor is connected to the gate of the first biasing transistor; a drain of the fourth biasing transistor, a drain of the fifth biasing transistor, and a gate of the fifth biasing transistor are connected in common; a source of the fifth biasing transistor, a drain of the sixth biasing transistor, and a gate of the sixth biasing transistor are connected in common; and a drain of the sixth biasing transistor is connected to a gate of the second amplifier transistor via a third resistance.
 36. The integrated circuit according to claim 35, wherein the first amplifier transistor, the second amplifier transistor, the first switching transistor, the third biasing transistor, the fifth biasing transistor, and the sixth biasing transistor are n-channel field effect transistors, and the second switching transistor, the first biasing transistor, the second biasing transistor, and the fourth biasing transistor are p-channel field effect transistors.
 37. An integrated circuit, comprising: a first amplifier transistor including a gate and a source, the first amplifier configured to amplify an input signal; a second amplifier transistor including a gate and a source and connected in series to the first amplifier transistor; a biasing circuit configured to supply a first bias voltage to the gate of the first amplifier transistor and supply a second bias voltage to the gate of the second amplifier transistor; an electrostatic protective circuit including a first resistance and a first switching transistor, wherein the first resistance is electrically connected between a first power source and a gate of the first switching transistor, and the first switching transistor is electrically connected between the gate of the second amplifier transistor and a second power source, and configured to control the second amplifier transistor.
 38. The integrated circuit according to claim 37, wherein the first switching transistor is configured to input the second bias voltage or the second power source to the gate of the second amplifier transistor.
 39. The integrated circuit according to claim 38, wherein the first resistance is connected between the first power supply and the gate of the first switching transistor via a first inverter and a second inverter.
 40. The integrated circuit according to claim 39, wherein a drain of the second amplifier transistor is electrically connected to the first power source via a diode, and the first power source is electrically connected to the second power source via a plurality of diodes. 